The bits-extras package

This package contains efficient implementations of high-level bit operations
missing from Data.Bits. The implementation is based on GCC builtins, which
translate to specialized instructions where available.

All operations in this package can also be (less efficiently) implemented in
terms of Data.Bits operations.

Issues: A GCC-provided library, libgcc_s, is dynamically linked to
provide software fallbacks on architectures without instructions
corresponding to specific operations. This is currently only expected to work
on Linux systems, and even there can lead to issues with GHCi's custom
linker. A workaround for GHCi on a linux system: ln -s /lib/libgcc_s.so.1
/lib/libgcc_s.so.

The current plan for broader support is to replace the libgcc dependency with
built-in fallbacks in C or Haskell code. This needs to closely follow GCC's
fall-back behaviour for each architecture. Alternative ideas would be
appreciated.